Genetic Factors In Aggression Flashcards
Genetic transmission
-Believed that agg is genetically inherited AT There’s no single gene that will make someone agg persons genetic makeup may interact with the env to = agg in certain situations. TF R’s use twin and adoption studies to assess validity of beliefs -Assumed twins share same env; if CR (extent to which both twins share same beh) for MZ twins ^ for agg this should be due to genetic influences as DZ twins share just environments. -Few TS specifically studied genetic transmission of agg, instead studying general anti-social behaviour bc agg d2d. -AS compare rates at which AC share beh with their AP (share env) and their BP (share genes not environment with). If CR between child and AP is ^ probably an env influenced beh. but if CR for beh ^ between child and BP then probably a genetically influenced beh
Coccaro: 40-50-70 McGuffin et al: difficulty entangling nature from nurture
-Found Genes = 40% of differences BT individuals in agg beh. //env accounts for 50% of ID in physical agg and 70% of ID in verbal agg. RTC genes account partly for whether or not P become agg but env P brought up in sig influences how this agg manifests -Found CR (agg/ASacts) of 87% for MZ and 72% for DZ. -TF indicating strong genetic transmission as MZ CR was higher. -// env impact as MZ CR not 100%, and DZ CR V high (above 50%) -highlights difficulty of entangling nature from nurture in agg studies
Equal environments argument
-Questionable to argue that ALL twins have equal environments. -R found MZ treated more similarly by parents, teachers + peers because they look more alike than DZ and are same gender. -vCR for agg in DZ exp ARO differential treatment rather than fewer shared genes. -Env influence need be considered when studying GT of Aggression
Button et al: Gender bias
-Inherent gender bias as most R = male only samples. -When generalised to wider pop over half of pop ignored, this makes conclusions questionable as M/F biologically different in the effect their genes have on expressing aggression. -Button et al: 258 TP aged 11-18 -Found heritability of agg anti-social acts sig^ in F than M contrary to common belief. -FM imply that agg in M may be bc of stronger env influence than F
Hutchings et al: Danish violence Ferguson et al: abandoned
-Studied agg in 14000 Danish Adoptees. -Found sig +ve correlation between # of convictions for criminal violence in BP (fathers particularly) and sons who’d been adopted -compelling evidence for a biological nature of agg. -// Ferguson et al argues there are inherent methodological issues in such adoption studies: -^agg at time of adoption/link between Agg parents and children may be ARO modelling aggression prior to adoption or emotional factors such as “feelings of abandonment”. -This limits the conclusions that can be drawn from such studies as they do not adequately control extraneous variables.
Brennan: VCH
-R into link between genetics and violent crime = mixed results -Conducted study comparing CH of AB with both BF and AF’s CH. -Found ^rates VC in adoptees = both when BP or AP had a VCH -Found more sig genetic influence in property crime but not in VC. -Shows a Biosocial interaction of genes and environment.
Candidate MAOA gene.
-Recently Psychologists ID candidate gene on x chr encoding for neural enzyme Monoamine Oxidase A (MAOA). -Enzyme produced breaks down important NT (Sr, DA and NA; ctrl mood, agg and pleasure circuits) after they carry impulses CS. -//vMAOA = imbalance of NT = abnormal buildup in PFC. -Build up (Sr) = violent reaction to stressful situations,. -Believe fault in gene responsible for producing MAOA = agg beh.
Brunner et al: Violent Dutch
-Study 28 male members of Dutch fam; several gens history agg/VC -Found ‘marker’/glitch on X chro V close to location of MAOA gene. -Marker present for all violent men but not for non-violent ones. FM urine tests = AL of NT/ Vv levels of MAOA by-product = v MAOA -TF believed agg beh ARO AL of Sr, Da, Na bc of defective MAOA. -//Brunner agrees unlikely direct link BT single gene and SSB -More probable that genetic deficiencies exert some influences on people’s behaviours rather than being sole cause for it.
Morley et al: reductionism
-QT OS a complex behaviour to solely genetics. -M argue; can infer CaE from isolation of candidate gene, ignores important env factors which may be just as if not more influential. -ie Brunners study: M agg could be attributed to Slt, specifically bad parenting and inappropriate role modelling. -TF reductionist view of candidate gene ignore other potential contributing factors.
RWA: VC rehab
-^understanding of GC in agg applicable to offender rehab = RWA -Bio Tx used to remedy inherited defects causing imbalanced NT. -// legal implications be diminished responsibility removes blame for violence TF careful consideration needed.
